Various methods of developing a latent image have been described in the art of electrophotographic printing and copying systems. Of particular interest with respect to the present invention is the concept of Contact Electrostatic Printing (CEP), which includes a variety of related liquid xerographic methods. In one process, an electrostatic image is produced on a image bearing member. The image bearing member is then coated with a uniform layer of liquid toner. Preferably, this layer of liquid toner is a thin and substantially uniform layer of high concentration liquid developing material. The toner layer is split image-wise between the image bearing member and an image separator, followed by transfer from the image separator to an image substrate such as paper. The development of the latent image occurs upon separation of the image bearing member and image separator surfaces. The development occurs as a function of the electric force strength generated by the latent image. In this process, toner particle migration or electrophoresis is replaced by direct surface-to-surface transfer of a toner layer. The particle migration is induced by image-wise forces. For the present description, the concept of latent image development via direct surface-to-surface transfer of a toner layer via image-wise forces will be identified generally as Contact Electrostatic Printing (CEP).
Generally, methods including CEP, are set forth in U.S. application Ser. No. 08/883,292 filed Jun. 27, 1997, entitled, "Electrostatic Latent Image Development;" U.S. application Ser. No. 08/884,236 filed Jun. 27, 1997, entitled "Image-wise Toner Layer Charging Via Air Breakdown For Image Development;" and U.S. application Ser. No. 09/004,629 filed Jan. 8, 1998, entitled "Image-wise Toner Layer Charging for Image Development." The disclosures of these references are hereby incorporated by reference in their entirety.
The image separator must have sufficient release properties to adequately release the developed image to a print substrate, such as paper. The image separator must also be conformable enough to transfer to rough print substrates. Additionally, since transfix is desirable in CEP, the image separator preferably is stable at temperatures of up to about 125.degree. C.